Generator neutral ground monitoring system and method

Patent metadata

Field	Value
Publication number	US-9500710-B2
Application number	US-201213651646-A
Country	US
Kind code	B2
Filing date	Oct 15, 2012
Priority date	Oct 15, 2012
Publication date	Nov 22, 2016
Grant date	Nov 22, 2016

Abstract

Fault analysis and detection involving a generator neutral ground includes monitoring a voltage waveform across a neutral grounding transformer of a generator. During monitoring of the voltage waveform a sample of the voltage waveform is acquired. Previously, a number of similar past samples of the monitored waveform were acquired and stored as well. The present sample is compared to one or more of these stored, past samples so that, based on a similarity between the present sample to the past samples, a generator fault indicated by the present sample can be identified. Identifying the generator fault can include recognizing that it is presently occurring or that it may occur in a predictable timeframe. Additionally, identifying a component of the generator that caused, or will cause, the generator fault can be identified as well. A diagnostic message or control signal based on the identified generator fault can then be generated.

First claim

What is claimed is:

1. A method comprising:
monitoring a voltage waveform across a second winding of a neutral grounding transformer of a three-phase generator, wherein the three-phase generator comprises a neutral bus bar, and the neutral grounding transformer comprises a primary winding and the second winding, the primary winding electrically coupling the neutral bus bar to ground;
acquiring a present sample of the voltage waveform;
comparing the present sample to one or more of a plurality of past samples of the voltage waveform;
based on a similarity between the present sample to the one or more past samples, identifying a generator fault associated with the present sample;
generating an operational control signal for the three-phase generator based on the generator fault.

2. The method of claim 1 , wherein identifying the generator fault includes determining that the present sample indicates that the generator fault has occurred.

3. The method of claim 1 , wherein identifying the generator fault includes predicting a future timeframe in which the generator fault will occur.

4. The method of claim 1 , wherein identifying the generator fault includes determining a component related to the generator fault.

5. The method of claim 4 , wherein the component includes stator winding insulation.

6. The method of claim 1 , further comprising:
storing the plurality of past samples of the voltage waveform in a database system.

7. The method of claim 1 , wherein acquiring a present sample includes:
converting the present sample from an analog signal to a digital signal;
converting the digital signal from a time-domain signal to a frequency-domain signal; determining at least one attribute related to the frequency-domain signal.

8. The method of claim 1 , further comprising:
converting the present sample from an analog signal to a digital signal;
performing component analysis on the digital signal; and
generating from the component analysis one or more vectors characterizing the digital signal.

9. The method of claim 1 , wherein identifying the generator fault includes considering power plant operating conditions in conjunction with the present sample and the one or more past samples.

10. The method of claim 1 , further comprising:
predicting an expected waveform of the present sample based on the one or more past samples.

11. A system comprising:
a voltage monitoring circuit configured to monitor a voltage waveform across a second winding of a neutral grounding transformer of a three-phase generator, wherein the three-phase generator comprises a neutral bus bar, and the neutral grounding transformer comprises a primary winding and the second winding, the primary winding electrically coupling the neutral bus bar to ground;
a signal receiver configured to acquire a present sample of the voltage waveform; a comparator configured to compare the present sample to one or more of a plurality of past samples of the voltage waveform;
a fault analyzer configured to identify a generator fault associated with the present sample based on a similarity between the present sample to the one or more past samples; and
a signal generator configured to generate an operational control signal for the three-phase generator based on the generator fault.

12. The system of claim 11 , wherein the fault analyzer is configured to determine that the present sample indicates that the generator fault has occurred.

13. The system of claim 11 , wherein the fault analyzer is configured to predict a future timeframe in which the generator fault will occur.

14. The system of claim 11 , wherein the fault analyzer is configured to determine a component related to the generator fault.

15. The system of claim 14 , wherein the component includes stator winding insulation.

16. The system of claim 11 , further comprising:
a database system configured to store the plurality of past samples of the voltage waveform.

17. The system of claim 11 , further comprising:
an analog to digital converter configured to convert the present sample from an analog signal to a digital signal;
a Fourier transformer configured to convert the digital signal from a time-domain signal to a frequency-domain signal; and
a signal analyzer configured to determine at least one attribute associated with the frequency-domain signal.

18. The system of claim 11 , further comprising:
an analog to digital converter configured to convert the present sample from an analog signal to a digital signal; and
a component analyzer configured to generate one or more vectors characterizing the digital signal.

19. The system of claim 11 , wherein the fault analyzer is configured to receive and utilize power plant operating conditions in conjunction with the present sample and the one or more past samples.

20. The system of claim 11 , wherein the fault analyzer is configured to predict an expected waveform of the present sample based on the one or more past samples.

Assignees

• Thompson Edward D
• Lau James F
• Siemens Energy Inc

Inventors

• Thompson Edward D
• Lau James F

Classifications

• G01R31/343 Primary

  in operation · CPC title

• G01R31/025

  Physics · mapped topic

• G01R31/52

  Testing for short-circuits, leakage current or ground faults · CPC title